Apparatus for lifting a hatch which can pivot around a pivot axis, especially a hatch of a motor vehicle, by means of a piston-cylinder unit. The piston-cylinder unit has a closed cylinder filled with a pressurized fluid, the interior of the cylinder 6 being divided by a piston into a first working chamber and a second working chamber. A piston rod passes through the second working chamber and is guided to the outside through a seal at the end of the cylinder and then hinged to the hatch, whereas the other end of the cylinder is hinged to a stationary component. A through-opening leading from the first working chamber to the second working chamber, is provided in the piston. The through-opening can be opened by an electrically actuated valve.